1. Field of the Invention
The present invention relates generally to data storage drives, and particularly to a method and apparatus for dynamically altering the accessing of storage drives based on the technology limits of the drives. Still more particularly, the present invention provides a method and apparatus which permits using low duty cycle drives for high duty cycle applications without using write duty cycle throttling or needing drive recovery.
2. Background of the Invention
A data storage subsystem is a peripheral of a computer system and is used to store data for the computer system. A data storage subsystem typically includes one or more disk or tape drives and a controller for managing the drives included in the storage subsystem. A data storage subsystem is not a stand alone computer system. Although a storage subsystem does execute an operating system, users may not interact directly with the storage subsystem. A user may interact directly with computer systems, but may not interact directly with a data storage subsystem.
Disk drives are designed to operate up to a maximum access rate. Thus, some drives are implemented with a technology that is considered to be low duty cycle such that the maximum access rate is low; while other drives are implemented with a technology that is considered to be high duty cycle with higher access rates. High duty cycle technology drives can be accessed reliably more rapidly than the low duty cycle technology drives. When a low duty cycle disk drive is used for high duty cycle applications that execute accesses more rapidly, data being written on the drive can be corrupted. The data corruption occurs because the head on a disk drive, which is designed using a technology that supports only slower accesses, is exposed to a heavy write activity that exceeds the upper limits of the low duty cycle technology. The head gets hot which results in bad data being written to the disk drive. This problem results in disk media failure which results in loss of the disk drive. The heat problem can also be caused in a similar manner by heavy read activity.
The prior art solution to fix this problem is to throttle the disk drive write activity by keeping track of the write duty cycle on a drive within a particular period of time. This approach addresses the problem after the problem has already occurred at the disk drive.
Therefore, the current technology would be improved by a method and apparatus for dynamically altering the accessing of storage drives based on the technology limits of the drives.